The Methodology and Statistics Core performs six main tasks essential to achieving the Center's mission. The tasks are: 1) Conduct psychometric analyses of all instruments used in CEDAR to ensure their quality; 2) Evaluate potential threats to the validity of results that could be caused by bias associated with proband ascertainment strategy, cohort effects, protocol implementation, and attrition; 3) Spearhead the development and psychometric analyses of the biobehavioral and environmental constructs contributing to derivation of the substance use disorder (SUD) liability index; 4) Conduct the statistical analyses to test CEDAR's biopsychosocial theory of SUD etiology; 5) Elucidate the relative contribution of the different facets of alcohol, tobacco, other drugs consumption topology in SUD risk and outcome; and, 6) Determine the validity and heuristic utility of quantifying the various DSM diagnostic categories of SUD. These interrelated tasks, requiring extensive synergy among the Center's cores and research modules, constitute essential operational requirements for satisfying CEDAR's mission.